1. Field of the Invention
This invention relates to an automatic surveying apparatus using a laser beam for making a route survey in road building, tunneling work and so on with great accuracy.
2. Description of the Prior Art
A survey for measuring long distances is indispensable for the fieldwork in constracting a road, pipe arrangement and so on or tunneling work. Compared with the fieldwork as described, the tunneling work which is restricted by space and requires high accuracy of the measurement adopts neither a method of traverse survey nor a method of triangulation.
In recent years, laser measuring apparatuses have been extensively adopted in the field of surveying. Of conventional measuring apparatuses to be applied to the shield method for excavating a tunnel while advancing a short cylinder (shield machine), there have been proposed various position-measuring apparatuses in which positional measurement is accomplished by directing a laser beam from a laser device located at the entrance of the tunnel onto a target fixed on the shield machine or an excavator located at the pit face of the tunnel, and detecting a laser spot formed on the target by the laser beam to obtain the positional deviation of the target which is caused by the movement of the shield machine. In the conventional measuring apparatuses, a projection screen on which a laser beam is projected to make a spot is mechanically moved in the direction perpendicular to the optical axis of the laser beam by the amount of positional displacement of the laser spot on the screen under observation using an image pick-up camera, thereby to detect the positional deviation of the target relative to the datum point for surveying. This method inevitably leads to mechanical errors, thereby involving decrease in measuring accuracy. In addition, the measuring accuracy may be further decreased due to the optical aberration of lenses used in the apparatus.
There has been proposed another apparatus in which the positional deviation of a laser spot which is formed on the projection screen by directing a laser beam thereon is detected by use of a solid-state image pick-up camera such as a CCD camera (Japanese Patent Application Disclosure Sho. No. 57(1982)-96213). This apparatus involves mechanical errors in measurement similarly to the foregoing prior art apparatus and requires rare technical skill when a survey is accomplished.
One of the inventiors of this invention previously proposed a position measuring apparatus disclosed in Japanese Patent Application Disclosure Sho. No. 56(1981)-104209, which enjoys high accuracy of measurement and is easy to handle.
The conventional measuring apparatuses including the apparatus proposed earlier by one of the inventors are disadvantageous in that they call for the work of surveying which proves to be troublesome when a survey of a sharply curved route is accomplished, because turning work for moving the laser device to a subsequent reference point for surveying consumes much time and labor. Besides, the conventional apparatuses entail decrease in measuring accuracy and can detect only positional deviation relative to the datum point at which the laser device is located, but cannot measure angular deflections (pitching and yawing) of the moving target relative to the optical axis of the laser beam issued from the laser device.